The aim of this research is to delineate the role of nerve pathways involving the abdominal prevertebral ganglia in controlling mesenteric blood vessels and to determine the organization of the abdominal nerve-vessel system. Experiments have been designed to determine: (1) the organization of the sympathetic outflow to branches of the inferior mesenteric and celiac arteries and the inferior mesenteric and portal veins; (2) whether or not there are afferent pathways from the mesenteric vasculature to neurons in the prevertebral ganglia; (3) whether there are reflexes between different vascular regions in the mesentery and/or between the mesenteric vasculature and the musculature of the gastrointestinal tract; (4) the nature of neuroeffector transmission from the postganglionic fibers of the prevertebral ganglia to mesenteric vascular smooth muscle cells. These studies will involve anatomical, physiological and pharmacological approaches to these questions. In vitro preparations from guinea pigs, rabbits and cats that consist of the celiac plexus and inferior mesenteric ganglion attached to selected abdominal organs will be used. Preganglionic, postganglionic and afferent nerve fibers will be electrically stimulated. Electrophysiological techniques will be used to determine intracellular responses of neurons in the prevertebral ganglia and vascular smooth muscle cells. Pressure recording techniques will be used to distend and record the contractile responses of mesenteric vascular and gastrointestinal segments. Pharmacologic techniques will be used to determine the mechanisms which modulate neurotransmission in the ganglia and to the blood vessels to determine how these mechanisms can be altered with drug therapy. The goal of these studies will be to understand how the autonomic nervous system controls blood vessels and what role reflexes between the viscera plays in this control. This knowledge will help us to understand and design better treatment for diseases which involve the autonomic nervous system; the nerves themselves as well as the organs they innervate.